Download The Neural Control of Movement

The Neural Control of
Movement
Introduction
The central nervous
system consists of the
brain and spinal cord
The nervous system is
involved in sensation,
interpretation, and
execution
The Neuromuscular System in
Exercise Science
Nervous system
– Peripheral nervous
system (PNS)
– Central nervous system
(CNS)
Motor neuron causes
muscle to contract
Whole structure
comprised of a single
motor neuron and all of
the muscle fibers
connected to that motor
neuron a motor unit
Communication Among Nerve Cells
Each connection of two
neuron is called a
synapse
Nerve impulse arrives
the end of one neuron, it
cause a chemical to be
release called
neurotransmitters to
produce (EPSP or IPSP)
Communication Between Nerve Cells
and Muscle
The connection between a
motor neuron and a muscle
fiber, called the
neuromuscular junction
Impulse in the motor neuron
originates in the spinal cord
While it travel to the end of
the neuron when it causes
the release of transmitter
called acetylcholine
EMG: Muscle Electrical Activity
Measure electrical
energy generated by
other biological tissues
– Heart (ECG; EKG)
– Brain (EEG)
– Muscle (EMG)
How do we control force generation
Control the level of
muscular force chiefly
through two mechanisms
– Change the # of motor units
activated by the brain
– Change frequency those
motor units are activated
More motor units and faster
rate of motor unit activitygreater EMG activity that
can be recorded
How we balance during normal
movement
Activates the muscles
necessary to maintain balance
first, then
Activates the muscles needed
to perform movement
(purposive activity - a
movement performed with a
clear aim)
Can measure priority scheme
by EMG methods
Brain uses a priority system
for the jobs it has to maintain
balance and postural stability
Interaction Between Performer and
Environment
The PNS receives and sends information from
the real world to the brain, and the brain has
the responsibility of sorting out what’s
important and what’s not.
The nervous system uses structures called
receptors to determine the status of thins in the
real world.
Vision
Is important for many of
the motor skills
Visual acuity
– acuteness or clearness of
vision
– Static VA: the ability of
the lens to change shape
– Dynamic VA: the ability
to discriminate objects
while they are moving
peripheral vision is a
part of vision that
occurs outside the very
center of gaze. There is
a broad set of noncentral points in the
field of view that is
included in the notion of
peripheral vision
Depth perception is the
visual ability to perceive
the world in three
dimensions (3D) and the
distance of an object.
Depth perception is a
binocular or stereoscopic
skill
Is determined from the
brain’s ability to combine
information received
from both eyes
Visual Control of Movement
Vision is often called the dominant sense
– Kids keep their eyes locked on the bouncing as dribble a
basketball
Skilled ball player seldom needs to look at the ball
while dribbling
Kinesthetic sense
– The ability to determine limb and body position in position
– Allows a skilled dribbler to predict the moment-to-moment
position of the ball
Visual Tracking
Muscles position the eye in
the socket and determine
where we focus our vision –
smooth pursuit
– The mechanism of choice for
following slowly moving
objects
Very rapid eye movement
are performed using
saccades to focus on the
new object of interest
Kinesthesis
The ability to perceived the position of the
body and limbs in space
The anatomy and physiology of
kinesthesis
The most important
receptor is called the
muscle spindle
– Detects length change of
muscle and sends neural
impulses to the rest of
the nervous system
When the brain gets the
information about the
current length of the
muscle, it can decide
how to continue the
movement
Joint receptor are
located in joints like the
knee and hip joints
– Contains small nerve
fibers that are sensitive
to a particular joint angle
Vestibular system is a
series of canals and
other small organs in the
inner ear
– Sensitive to changes in
motion
– Small hair cell floating in
a specialized fluid snese
this motion if accelerate
up or down, forward,
backward
The Kinesthetic System in Motor
Learning
Kinesthetic sense can be
important when
acquiring new motor
skills
Kinesthetic sense can be
improved with practice
The Use of Feedback in Skill
Acquisition
Motor program
– A set of instructions for
performing a particular
task
Requires time to send
information from the
limbs to the brain, and
the brain needs time to
process the information
it receives and send a
correction back to the
working muscle
Feedforward Control for rapid
Movements
When the fastest human
movements, there may
not be enough time to
make midcourse
corrections
Very rapid movements
called ballistic
movement and are
preprogrammed
– Once the ballistic
movement begins, it
continues until the motor
program plays itself out
Control by cerebellum
During rapid movement agonist muscle is
activated first, and antagonist muscle is
activated to protect the limb from high force
(muscle injury)
Movement performed in the absence of
feedback are open-loop
– No circuit from the muscle or spinal cord to brain
center
– Movement is too fast to allow any information
from the peripheral receptors to be effective
The Neuroscience of Motor Learning
The human brain
consists of 1013 neurons
Habituation
– as a decrease in an
elicited behavior
resulting from the
repeated presentation of
an eliciting stimulus (a
simple form of learning).
– When aplysia learns the
stimulus that is not
longer a threat
B
A
A
B
Memory for the movement is stored in synapse
Repeated activation results in a change in the
ability of the information to cross the synapse
from sensory neuron to motor neuron
Synaptic plasticity
– The ability of the synapse to change
Important areas for motor
learning is the cerebellumcontains a dense layer of
cells involved in skilled
movement, particularly in
the outer layer of the
cerebellum called
cerebellum cortex
Purkinje cell in cerebellar
cortex has a cell body
with a large number of
denrites
The dendritic spines
contain small processes
called dendritic spines
Brain Plasticity
PET study showed
cerebral blood flow in
left sensorimotor cortex
after 1 hour of practice
Neural activation plays
in changing muscle
fiber characteristics(Buller & Lewis 1965)
The Time of Motor Activity
Reaction time can be defined as the time
interval between the stimulus and the initial
response
Reaction time provides an overall appraisal of
the ability to receive and process auditory,
visual, kinesthetic, or other types of sensory
information, and begin to
execute the appropriate
movement
Anatomy of a reaction time task
Visual stimulus to eyes
receptor →brain’s
cerebral cortex →motor
cortex (movement
planning) →motor cortex
neurons synapse on motor
neurons in spinal cord
(activate the responding
muscles)
Anticipation Timing
Timing of motor activity is important to proper
execution
– A movement too soon or too late and the ball will
end up in foul territory
Requires players to make judgment about the
velocity of the ball, the path the ball is follow
etc
A continued neural processing, brain has to try
to continually update this information
Discussion
Could you take a example to explain a use
feedback in skill acquisition in a given
movement.
What is the importance of visual control of
movement and kinesthetic sense in sports.
How you train these bio-abilities.
In your viewpoint, a good balance (equilibrium)
during normal movement would reflect a
health status in aged people. Why?
Could you design a research topics on the
neural control of movement.